1. Field of the Invention
The invention relates to an X-ray detector which has a casing to which a vacuum can be applied, an input screen provided with a luminescent coating and an output screen able to give location-sensitive read-out. The invention also relates to an X-ray examination apparatus for medical diagnoses provided with such an X-ray detector.
2. Description of the Related Art
An X-ray detector of this type is disclosed in EP-A-450,670, which corresponds to U.S. Pat. No. 5,138,147. In the detector described in this patent, image detection is obtained by conversion of an image-carrying X-ray beam, via luminescence, into an image-carrying beam of photo-electrons. The photo-electrons are accelerated over a vacuum gap and electrons accelerated in this way are either detected directly via electron-sensitive diode elements or converted in a phosphor coating into light which is detected via a light-sensitive diode matrix. In both cases use is made of a TFT switching matrix for location sensitivity.
In the case of read-out using a photodiode matrix, the amplification variation desired for medical X-ray examination is difficult to achieve with a detector of this type. Furthermore, in this case the technological problem arises that the diodes usually are not well able to withstand a high heating temperature desired for other purposes.
In principle, the desired amplification variation can be achieved with an electron-sensitive diode matrix read-out, but as yet factory production of such a diode matrix does not appear to be easy.